MARTINEZ — Residents here and in Pacheco awoke Friday to a public health advisory after an incident at the Shell Refinery, officials said.

The advisory, which lasted until about 9:10 a.m., came after an issue with a “unit upset,” at the refinery, the company said. The Contra Costa County Sheriff’s Office’s Community Warning System issued the advisory around 5:45 a.m.

A Shell spokeswoman said a “unit upset” occurs when part of the operations on a project are not up to standard, but wouldn’t comment further.

“Out of caution, we’ve called a Community Warning System level 2,” a statement from the company posted on its social media sites said, referring to the warning that went out to residents. “To this point, we have not seen anything on our fence line monitors or through our community monitoring” to indicate residents are affected.”

According to the advisory, residents were warned of eye, skin, nose or throat irritation.